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LaTeX is defined to be a set of commands that are run by a TeX implementation (see Overview). This section gives a terse overview of the main programs (see also Command line).
latex
pdflatex
In TeX Live (http://tug.org/texlive), if LaTeX is invoked
via either the system command latex
or pdflatex
,
then the pdfTeX engine is run (http://ctan.org/pkg/pdftex).
When invoked as latex
, the main output is a .dvi
file; as pdflatex
, the main output is a .pdf file.
pdfTeX incorporates the e-TeX extensions to Knuth’s original
program (http://ctan.org/pkg/etex), including additional
programming features and bi-directional typesetting, and has plenty of
extensions of its own. e-TeX is available on its own as the system
command etex
, but this is plain TeX (and produces
.dvi).
In other TeX distributions, latex
may invoke e-TeX
rather than pdfTeX. In any case, the e-TeX extensions can be
assumed to be available in LaTeX.
lualatex
If LaTeX is invoked via the system command lualatex
, the
LuaTeX engine is run (http://ctan.org/pkg/luatex). This
program allows code written in the scripting language Lua
(http://luatex.org) to interact with TeX’s typesetting.
LuaTeX handles UTF-8 Unicode input natively, can handle OpenType
and TrueType fonts, and produces a .pdf file by default.
There is also dvilualatex
to produce a .dvi file,
but this is rarely used.
xelatex
If LaTeX is invoked with the system command xelatex
, the
XeTeX engine is run (http://tug.org/xetex). Like LuaTeX,
XeTeX natively supports UTF-8 Unicode and TrueType and OpenType
fonts, though the implementation is completely different, mainly using
external libraries instead of internal code. XeTeX produces a
.pdf file as output; it does not support DVI output.
Internally, XeTeX creates an .xdv
file, a variant of DVI,
and translates that to PDF using the (x
)dvipdfmx
program, but this process is automatic. The .xdv
file is only
useful for debugging.
Other variants of LaTeX and TeX exist, e.g., to provide additional support for Japanese and other languages ([u]pTeX, http://ctan.org/pkg/ptex, http://ctan.org/pkg/uptex).